China wholesale Hex Bolt A490 - American Thread – Ji Luo Fastener

American thread
American thread, also known as unified thread. In 1864, Willian Sellers, an American, formulated the National Thread (N) according to the Wyeth Thread Standard System of the United Kingdom. These two threads are similar in diameter and pitch series and tolerance.
General purpose of trapezoidal thread , American standard ANSIB1.5 tooth profile angle is 29 degrees, British drive threads (dimensions and tolerances) All diameters and pitch combinations calculated using the same formula as the standard series, excluding those outside the standard series.